The epithelial membrane protein-2 (EMP2) is a member of the growth arrest specific-3/peripheral myelin protein-22 (GAS3/PMP22) family of tetraspan proteins. Other four-transmembrane families, connexins and tetraspanins, play roles in gap junctions, cell-cell recognition processes, and intracellular trafficking. Less is known about the GAS3/PMP22 family. The information available mainly relates to their potential roles in various diseases. For instance, mutations in the prototypic GAS3 family member PMP22 have been found to cause neurodegenerative disease (i.e., Dejerrine Sottas Syndrome and Charcot Marie Tooth Syndrome). EMP2 has also been implicated in B cell tumor progression and stress-induced apoptosis.
EMP2 is expressed at high levels in epithelial cells of the lung, eye, and genitourinary tracts. Like several tetraspan proteins (CD9, CD81, PMP22), EMP2 in murine fibroblasts is localized to lipid raft domains. EMP2 controls cell surface trafficking and function of certain integrins, GPI-linked proteins, and class I MHC molecules, and reciprocally regulates caveolin expression. (see, Claas et al., J Biol Chem 276:7974-84 (2001); Hasse et al., J Neurosci Res 69:227-32 (2002); Wadehra et al., Exp Mol Pathol 74:106-12 (2003); Wadehra et al., Mol Biol Cell 15:2073-2083 (2004); Wadehra et al., J Biol Chem 277:41094-41100 (2002); and Wadehra et al., Clin Immunol 107:129-136 (2003)).
Detailed studies of the subanatomic distribution of EMP2 in murine and human ocular tissue indicate that EMP2 is localized to epithelial layers of the cornea, ciliary body, and retinal pigmented epithelium-choroid, the stromal layers of the sclera, and the nerve fiber layer of the retina and optic nerve. This distribution is distinct from other TM4SF proteins and may relate to a role in apical membrane recycling.
Endometrial cancer (EC) is the most common gynecological malignancy. In the United States, the death rate from EC has doubled in the last twenty years, and currently a woman has approximately a 3% chance of developing EC during her lifetime (Silverberg et al., World Health Organization Classification of Tumors: Tumors of the Breast and Female Genital Tract, Lyon: IARC Press, p. 221-57 (2003); Sorosky J I, Obstet Gynecol 111:436-47 (2008)). EC is classified into two major sub-groups based on histology, clinical behavior, and epidemiology. The more common Type I is associated with estrogen predominance and pre-malignant endometrial hyperplasia (Hecht et al., J Clin Oncol 24:4783-91 (2006); Sherman, Mod Pathol 13:295-308 (2000)). Type II is mediated by non-hormonal risk factors, and often has a high grade or high-risk histology with an aggressive clinical course (Hecht et al., J Clin Oncol 24:4783-91 (2006)). Incidence of ECs generally increases with age, with 75-80% of new cases occurring in postmenopausal women (Creasman, Semin Oncol 24:S1-140-51-50 (1997)).
Primary treatment for ECs is the surgical removal of the tumor, but recurrence is common, and other therapeutic interventions (radiotherapy, chemotherapy, and endocrine therapy) benefit only a subset of patients (Markman, Semin Oncol 33: S33-8 (2006); Engleman et al., Semin Oncol 30:80-94 (2003)). Presently, there are few biomarkers that distinguish ECs at the pre-malignant stage, although emerging efforts are targeting molecules that underlie the process of tumorigenesis (Kelloff et al., Clin Cancer Res 12:3661-97 (2006); Gossett et al., Int J Gynecol Cancer 14:145-51 (2004)). Similarly, there are currently no biomarkers that can be targeted for tumor suppression and elimination. Thus, new modalities for early detection and treatment of ECs at premalignant and frankly malignant stages of disease are needed to improve management and prognosis.
One promising biomarker appears to be EMP2. EMP2 expression is associated with EMP2 neoplasia (Wadehra et al., Cancer 107:90-8 (2006)). In endometrial cancer, EMP2 is an independent prognostic indicator for tumors with poor clinical outcome. EMP2 positive tumors, compared to EMP2 negative tumors, had a significantly greater myometrial invasiveness, higher clinical state, recurrent or persistent disease following surgical excision, and earlier mortality. As EMP2 expression was independent of other known biomarkers such as the estrogen receptor and progesterone receptor (Wadehra et al., Cancer 107:90-8 (2006)), EMP2 represents a unique biomarker for patients who are not responsive to current hormone or chemotherapy. Moreover, EMP2 expression level positively correlates with the increasing pre-malignant potential of proliferative endometrium. That is, there is a gradation of endometrial EMP2 expression, with minimal expression in normal proliferative or quiescent premenopausal endometrium, and increasing expression in patients with disordered proliferative endometrium, endometrial hyperplasia, and endometrium carcinomas.
In the endometrium, EMP2 expression is regulated by progesterone and required for successful blastocyst implantation (Wadehra et al., DevBiol 292:430-41 (2006); Wadehra et al., Reprod Biol Endocrinol 6:15 (2008)). EMP2 appears to regulate trafficking of various proteins and glycolipids by facilitating transfer of molecules from post-Golgi endosomal compartments to appropriate plasma membrane locations. Specifically, EMP2 is thought to facilitate the appropriate trafficking of select molecules into glycolipids-enriched lipid raft microdomains (GEMs) (Wadehra et al., Mol Biol Cell 15:2073-83 (2004)). GEMs are cholesterol rich microdomains which are often associated with chaperones, receptosomes, and protein complexes that are important for efficient signal transduction (Leitinger et al., J Cell Sci 115:963-72 (2002); Moffett et al., J Biol Chem 275:2191-8 (2000)). Moreover, GEMs are involved in correct sorting of proteins from the Golgi apparatus to plasma membrane (Abrami et al., J Biol Chem 276:30729-36 (2001); Galbiati et al., Cell 106:403-11 (2001); Gruenberg et al., Curr Opin Cell Biol 7: 552-63 (1995)). In this respect, modulation of EMP2 expression levels or its location on the plasma membrane alters the surface repertoire of several classes of molecules including integrins, focal adhesion kinase, class I major histocompatibility molecules and other immunoglobulin super-family members such as CD54 and GPI-linked proteins (Wadehra et al., DevBiol 287:336-45 (2005); Wadehra et al., Clinical Immunology 107:129-36 (2003); Morales et al., Invest Ophthalmol Vis Sci (2008)).
Chlamydiae are obligate gram-negative intracellular prokaryotic pathogens that are responsible for significant human morbidity and infections of multiple organ systems. More than 90 million new cases of sexually transmitted, genitourinary Chlamydia trachomatis infection are reported annually. These infections are a significant cause of infertility, ectopic pregnancy, and chronic pelvic pain syndromes (Brunham & Rey-Ladino, J. Nat Rev Immunol 5:149-61 (2005)). Ocular infections with Chlamydia may result in trachoma, the primary cause of infectious blindness worldwide (see, Engel, Proc Natl Acad Sci USA 101:9947-8 (2004)), and Chlamydia species also have been associated with other inflammatory diseases (see, Hannu et al. Rheumatology (Oxford) 38:411-4 (1999), Gencay et al., Am J Respir Crit. Care Med 163:1097-100 (2001); Smieja et al., BMC Infect Dis 2:21 (2002); and Dautry-Varsat et al., Traffic 5:561-570 (2004)). The pathophysiology of Chlamydial infections is only partly understood, in particular identification of host cellular proteins involved in Chlamydial infection that may reveal new strategies for disease control.
Chlamydia has a unique biphasic developmental cycle. The first step in infection requires attachment of a metabolically inactive but infectious, spore-like structure called the elementary body (EB). The initial reversible attachment of EB to epithelial cell layers is proposed to involve a number of Chlamydial and host ligands and adhesions. Possible candidates for attachment mediation include major outer membrane protein (MOMP), heat shock protein 70, OmcB, heparin sulfate-like glycosaminoglycans, polymorphic outer membrane protein gene family (pmp), estrogen receptor complex, and caveolae. Upon cellular attachment local actin polymerization, elicited by intracellular secretion of EB products and tyrosine phosphorylation of various protein species leads to endocytosis of the attached EB. After a few hours, an internalized EB differentiates into the reticulate body (RB), a metabolically active, non-infectious form which gives rise to >1000 progeny EBs, followed by host cell lysis and release of infectious EBs that begin another life cycle (see, Engel, Proc Natl Acad Sci USA 101:9947-8 (2004); Dautry-Varsat et al., Traffic 5:561-570 (2004); Gabel et al., Infect Immun 72:7367-73 (2004); Davis et al., Proc Natl Acad Sci USA 99:9427-32 (2002); Raulston et al., Infect Immun 70:535-43 (2002); Finlay, et al., Science 276:718-725 (1997); and Virok et al., Infect Immun 73:1939-46 (2005)).
Chlamydial infection can result from oral, vaginal, or anal sexual contact with an infected partner. Chlamydia trachomatis can be sexually transmitted. In women, the pathogen can cause pelvic inflammatory disease (PID) with a risk of tubal obstruction and infertility. In men, the bacteria can cause epidydimitis and infertility. Chlamydia can also cause acute respiratory tract infections in humans. Infection of the eye with Chlamydia trachomatis, or trachoma, is a leading cause of preventable blindness worldwide. Chlamydial infections are a particularly serious health threat to newborns who contract occular infections at birth from infected birth canals of their mothers. If untreated, almost 50% of these children develop inclusion conjunctivitis and 20% develop systemic infection resulting in serious pneumonia. Chlamydia also is likely to exacerbate atherosclerosis. In particular, coronary heart disease has been associated with increased titers of Chlamydia antibodies. In addition, reactive inflammatory arthritis is a common sequel to sexually acquired non-gonococcal genital tract infection. Approximately 50% of reactive inflammatory arthritis cases are associated with Chlamydia trachomatis infection of the genital tract. Chlamydial infection can be asymptomatic and irreversible damage may have already occurred before treatment is sought.
Accordingly, Chlamydia is a serious public health concern around the world. However, Chlamydia is an intracellular pathogen which is difficult to treat. There is no robust vaccine for Chlamydia and conventional antibiotic therapies often fail to clear chronic infections.
Recent studies indicate that the interaction between Chlamydia and host cells occurs at specific cholesterol- and glycosphingolipids-rich lipid raft microdomains. Lipid rafts, often experimentally defined by their insolubility in cold non-ionic detergents are believed to be subspecialized cell membrane regions important in assembly of receptor signaling complexes, protein trafficking, endocytic and secretory pathways. Many other proteins associated with bacterial infection have been found in lipid raft compartments. Dautry-Varsat et al., Traffic 5:561-570 (2004); Simons et al., Nature 387:569-572 (1997); Gabel et al., Infect Immun 72:7367-73 (2004); Claas et al., J Biol Chem 276:7974-84 (2001); Brown et al. J Biol Chem 275:17221-4 (2000); and Subtil et al., J Cell Sci 117:3923-33 (2004); and Webley et al., BMC Infect Dis 4:23 (2004).
As reported herein, the Applicants have discovered that EMP2 is a useful target for anti-cancer therapy for cancers which express or overexpress EMP2 molecular cell entry and also that EMP2 is a cell entry point for Chlamydia. Accordingly, EMP2 polypeptides, anti-EMP2 antibodies, and EMP2 siRNA can be used to modulate the ability of Chlamydia to enter a host cell to cause infection and disease and can be used also to treat cancers expressing or overexpressing EMP2 As discussed above, there remains a large need for methods and compositions which are useful in the prevention, treatment, and modulation of Chlamydia infection as well as the prevention, diagnosis and treatment of cancer. Accordingly, this invention provides novel compositions and methods for meeting these and other needs.